Scepticism is a healthy attitude to adopt to many, if not all, untested propositions. Sceptics throughout history, by applying their reasoned judgment and hard-headed critical faculties, have exposed lies, delusions and superstition.

Which is why scepticism is entirely the wrong word to apply to those who deny that emissions of carbon dioxide from human activity are leading to rises in average global temperatures, with potentially disastrous consequences. True sceptics respond to evidence.

Last week more evidence was published to support the established case for man-made global warming. Research, led by the US National Oceanic and Atmospheric Administration, drew on data from 11 possible indicators of climate and found that each one suggested warming consistent with expected effects of rising concentrations of greenhouse gases. Snow cover in the northern hemisphere is shrinking, glaciers are retreating, sea levels are rising, oceans and the atmosphere are warming. As it was put by Peter Stott, head of climate monitoring at the Met Office, which participated in the study: "The fingerprints are clear".

The data in this study were not included in the 2007 UN Intergovernmental Panel on Climate Change report that has been the main target of attack by climate change deniers. The IPCC's authority was badly damaged by "climategate" – the leak of emails between scientists at the University of East Anglia, purporting to show a conspiracy to suppress inconvenient data.

In fact, as subsequent inquiries have shown, the emails proved at worst a cavalier and somewhat arrogant attitude on the part of scientists to critics of their work and a secretive, siege mentality in response to climate deniers. The actual scientific case for global warming was unscathed.

And yet, somehow the whole affair had a disproportionate effect in stifling public urgency over climate change. It did not help that the Copenhagen summit, shortly afterwards, billed in advance as the vital last chance opportunity for global action, resulted in an opaque compromise cobbled together at the eleventh hour mainly so heavyweight politicians in attendance could claim to have done some kind of deal.

That did little to advance the cause of public confidence or understanding. Since then, economic crisis and budget austerity have cleared pretty much all other considerations off political agendas in the developed world.

Democrats in the US Senate have now abandoned President Obama's climate bill, a modest affair to introduce some cap-and-trade mechanism to reduce emissions. Federal climate regulation now looks dead for the foreseeable future.

It is both baffling and sadly predictable that it should be so hard to turn a matter of near certain scientific urgency into political action. It is also profoundly depressing that the chances of concerted global action to protect the environment seem to be receding.

It is a marker of how far the environment has slipped down the public agenda in this country that neither David Cameron nor Nick Clegg has said anything of note on the subject since forming a government, while not long ago they did fierce battle for the title of greenest party leader.

Their claimed ambitions to take a lead on climate change really are a worthy object of scepticism.